Probably the reason why people are not using bitcoin as payment because of its volatility. If you buy a shoes worth .01 btc or roughly $60 and tomorrow that .01 btc will be worth $80 so that you just paid $20 over the price of that shoes. So that won't really mean good for you. So i think bitcoin being so volatile makes people not want to use it as payment.
Bitcoin needs to find a stable value. That value will probably be somewhere between 2000 and 3000 dollars. We are all hoping for the growth but for the Bitcoin to stabilize itself and people start using it as a source of the standard payments it should actually fall. This current price is so volatile and that isn't promising as a source of payment. Bitcoin is still very good for the investors that are accumulating it and using it as a profit gaining machine. I don't know for certain what the future will bring but for now, the shoes will still need to be bought with the FIAT.